Canid hybrid

Canid hybrids are the result of interbreeding between different species of the canine (dog) family (genus Canis). They often occur in the wild, in particular between domestic or feral dogs and wild native canids.[1]

When the differences in number and arrangement of chromosomes is too great, hybridization becomes less and less likely. The wolf, dingo, dog, coyote, and golden jackal all have 78 chromosomes arranged in 39 pairs.[6] This allows them to hybridize freely (barring size or behavioral constraints) and produce fertile offspring. There are two exceptions: the side-striped jackal and black-backed jackal.[7] Although these two theoretically could interbreed with each other to produce fertile offspring, it appears they cannot hybridize successfully with the rest of the genus Canis. A study of the maternal mitochondrial DNA of the black-backed jackal could find no evidence of genotypes from the most likely mates - the side-striped jackal nor the golden jackal - indicating that male black-backed jackals had not bred with these.[8] There is no evidence that the African wild dog hybridizes with any of them.[9]

Dog hybrids kept as pets are prohibited in certain jurisdictions, or are classed as wild animals and must be housed in the same way as purebred wolves.

In the United States legislation differs greatly from state to state. In New York, the law does not allow an individual to house or own a dog hybrid of any kind, even if there is a low percentage of wolf genes in the hybrid.[11] States such as Indiana and Arkansas allow the ownership of hybrid animals, but they regulate it strictly with health records, immunization records, and registration of the animal[12] while other states, such as Arizona, do not have any laws about owning a wolfdog hybrid.[12] States may or may not create their own laws regarding the issue of wolfdog hybrids.

The domestic dog (Canis lupus familiaris) is a domesticated form of the gray wolf (Canis lupus lupus) and therefore belongs to the same species as other wolves, such as the dingo (Canis lupus dingo). Therefore, crosses between these sub-species are biologically unremarkable and not a hybridization in the same sense as an interbreeding between different species of Canidae.

Wolves are different from domestic dogs in that wolves usually have slimmer chests, longer legs, and they also have stronger jaws than those of the domestic subspecies.[13] The difference in appearance from the wolf to the domestic dog becomes even larger when a mix of the two animals is created. Wolfdogs do not have one common description of their appearance because it varies from one breeding cycle to the next.[13] It differs from cycle to cycle because the number of wolf genes inherited in the animal differs greatly and is recorded in a percentage form. The general layout for describing the percentage of wolfdogs is as follows: 1-49% is considered low content (LC), 50-74% is considered to be mid-content (MC), and 75% and higher is considered to be high content (HC).[14] The percentage of the amount of wolf in a wolfdog decides what the animal will look like. For example, if a wolfdog is 25% husky and 75% wolf, it will appear more like a wolf than a husky because it contains more genes from the wolf.[11] This means that the appearance of the wolfdog will most likely contain a narrower chest, longer legs, and sharper teeth because it inherited more traits from the wolf parent.[15]

People wanting to improve domestic dogs or create an exotic pet may breed domestic dogs to wolves. Gray wolves have been crossed with dogs that have a wolf-like appearance, such as Siberian huskies, and Alaskan malamutes. The breeding of wolf–dog crosses is controversial, with opponents purporting that it produces an animal unfit as a domestic pet. A number of wolfdog breeds are in development. The first generation crosses (one wolf parent, one dog parent) generally are backcrossed to domestic dogs to maintain a domestic temperament and consistent conformation.

The dingo (Canis lupus dingo) breeds freely with other domestic dogs. This is now so widespread that in some areas, dingoes are now mostly mixed-breed dogs, crossed in recent times with dogs from other parts of the world. However, DNA study shows that "the dingo originates from domesticated dogs, originally from East Asia"[16] (which reverted to the wild) and so interbreeding between dingos and other domestic dogs is also not a hybridization in the same sense as an interbreeding between different species of Canidae.

Some dingo hybrids are accepted back into the wild dingo population, where they breed with pure dingoes. In some parts of Australia, up to 80% of dingoes are part domestic dog. Dingoes are distinguishable from domestic dogs through DNA and through having longer teeth and longer muzzles.

Coydogs (the offspring of a male coyote and female dog) are naturally occurring red or blond color variations of the coyote or were feral dogs. The breeding cycles of dogs and coyotes are not synchronized and this makes interbreeding uncommon. If interbreeding had been common, each successive generation of the coyote population would have acquired more and more dog-like traits.

Hybridization between gray wolf and coyote has long been recognized both in the wild and in captivity. In an evolutionary biology research conducted by a team of researchers in the Uppsala University, analysis of control region haplotypes of the mitochondrial DNA and sex chromosomes from Mexican wolves, a critically endangered subspecies of the grey wolf once nearly driven to extinction in the wild, confirmed the presence of coyote markers in some of the wolves.[17] The study suggests that at some point in time, female coyotes managed to mate with some of the male wolves of the remnant wild Mexican wolf populations. Analysis on the haplotype of some coyotes from Texas also detected the presence of male wolf introgression such as Y chromosomes from the grey wolves in the southern coyotes. In one cryptology investigation on a corpse of what was initially labelled as a chupacabra, examinations conducted by the UC Davis team and the Texas State University concluded based on the sex chromosomes that the male animal was in fact another coyote and wolf hybrid sired by a male Mexican wolf.[18]

DNA analysis consistently shows that all existing red wolves carry coyote genes. This has caused a problem for Canid taxonomy, as hybrids are not normally thought of as species, though the convention is to continue to refer to red wolves as a subspecies of wolf, Canis lupus rufus, with no mention of the coyote taxon, latrans.[19][20]

In recent history, the taxonomic status of the red wolf has been widely debated. Mech (1970) suggested that red wolves may be fertile hybrid offspring from gray wolf (Canis lupus) and coyote (C. latrans) interbreeding. Wayne and Jenks (1991) and Roy et al. (1994b, 1996) supported this suggestion with genetic analysis. Phillips and Henry (1992) present logic supporting the contention that the red wolf is a subspecies of gray wolf. However, recent genetic and morphological evidence suggests that the red wolf is a unique taxon. Wilson et al. (2000) report that gray wolves (Canis lupus lycaon) in southern Ontario appear genetically very similar to the red wolf and that these two canids may be subspecies of one another and not a subspecies of gray wolf. Wilson et al. (2000) propose that red wolves and C. lupus lycaon should be a separate species, C. lycaon, with their minor differences acknowledged via subspecies designation. North American wolf biologists and geneticists also concluded that C. rufus and C. lupus lycaon were genetically more similar to each other than either was to C. lupus or C. latrans (B.T. Kelly unpubl.). In 2002 orphometric analyses of skulls also indicate that the red wolf is likely not to be a gray wolf–coyote hybrid (Nowak 2002). Therefore, while the red wolf's taxonomic status remains unclear, there is mounting evidence to support C. rufus as a unique canid taxon.[21]

Classifying animals commonly referred to as "eastern coyotes" or "northeastern coyotes" has become a problem for taxonomists, as it is unclear what new taxon will be used to refer to this new population of animals.[22]

Three golden jackal-dog hybrids from Croatia. The discovery of these specimens confirmed that hybridization between the two species occurs in the wild, and that the two have unlimited fertility with each other.[23]

Although hybridization between wolves and golden jackals has never been observed, evidence of such occurrences was discovered through mtDNA analysis on jackals in Bulgaria.[24] Although there is no genetic evidence of gray wolf-jackal hybridization in the Caucasus Mountains, there have been cases where otherwise genetically pure golden jackals have displayed remarkably gray wolf-like phenotypes, to the point of being mistaken for wolves by trained biologists.[25]

Several years ago I saw confined in the Zoological Gardens of London a female hybrid from an English dog and jackal, which even in this the first generation was so sterile that, as I was assured by her keeper, she did not fully exhibit her proper periods; but this case, from numerous instances have occurred of fertile hybrids from these two animals, was certainly exceptional.[26]

Robert Armitage Sterndale mentioned experimental golden jackal/dog hybrids from British India in his Natural History of Mammals in India and Ceylon, noting that glaring jackal traits could be exhibited in hybrids even after three generations of crossing them with dogs[27]

In Russia, golden jackal/Lapponian herder hybrids were bred as sniffer dogs because jackals have a superior sense of smell and Lapponian herders are good cold climate dogs. Also, fox terrier, Norwegian lundehund, and Spitz blood were combined to create the Sulimov dog.[28] As well as a superior sense of smell, important at low temperatures where substances are less volatile and therefore less pungent, Sulimov dogs are small-sized and can work in confined spaces. When tired, their normally curled tails droop, making it clear to the handler that the dog needs to be rested. The jackal hybrids were bred by Klim Sulimov, senior research assistant at the D.S. Likhachev Scientific Research Institute for Cultural Heritage and Environmental Protection in Russia. Male jackal pups had to be fostered on a husky bitch in order to imprint the jackals on dogs. Female jackals accepted male huskies more readily. The half-breed jackal-dogs were difficult to train and were bred back to huskies to produce quarter-breed hybrids (quadroons). These hybrids were small, agile, trainable and had an excellent sense of smell. Twenty-five jackal-dog hybrids are used by Aeroflot at Sheremetyevo International Airport in Moscow for functions including bomb-sniffing. Their breeding program dates back to 1975, but it was not applied to bomb detection until 2002.